Field
Embodiments of the present disclosure generally relate to the fabrication of integrated circuits and particularly to the deposition of an amorphous carbon layer with high film density and high etch selectivity.
Description of the Related Art
Development of hardmask materials having high etch selectivity is a critical task for patterning new generation NAND and DRAM devices. Carbon-based materials, such as amorphous carbon (denoted as a-C), has been proved to be an effective material serving as etch hardmask for oxide, nitride, poly-Si, or metal (e.g., Al) materials due to its chemical inertness, optical transparency, and good mechanical properties.
To ensure that the desired amorphous carbon film adequately protects underlying dielectric stacks during the subsequent etching process, it is important that amorphous carbon film possesses a relatively high etch selectivity, or removal rate ratio, with respect to an underlying material layer. Higher etch selectivity is advantageous to transfer the patterns to underlayers accurately. One way to increase the etch selectivity is to densify the amorphous carbon film by increasing C:H ratio, which, however, results in high compressive film stress that may significantly impact the feature transfer during the lithographic process. High compressive film stress induces line bending of high aspect ratio structure or line breakage during the subsequent etching process, especially when the feature size shrinks to 20 nm and beyond.
Therefore, there is a need in the art for a hardmask with reduced compressive film stress, excellent etch selectivity, and line bending control.